Slavia started on the front foot, and Danijel Sturm had a golden chance to open the scoring inside 30 seconds. A single incisive pass carved the French side apart, and the 27-year-old advanced to the edge of the six-yard box, but he sliced his effort wildly out for a throw-in.
Sturm then turned provider, clipping a cross into Stepan Chaloupek, but the defender was unable to guide his header on target from a good position.
Lens steadily grew into the contest after the frantic start, although Samuel Isife had Robin Risser worried with an audacious effort from close to the halfway line, and the goalkeeper had to be alert to beat Šturm to another excellent through ball.
The Cervenobili could not make their dominance pay, and Lens enjoyed a spell of pressure as the half wore on. Former Slavia forward Abdallah Sima should really have put the visitors ahead against his old club, but he was unable to sort out his feet after Florian Thauvin’s pass had seemingly left the goal at his mercy.
Matthieu Udol then had a double chance from a corner, but Jakub Markovic repelled both the header and the follow-up effort. At the other end, Emmanuel Ayaosi thought he had given the Czech side a well-deserved advantage, but the referee spotted that the ball had struck his arm before he swept it into the net.
There was still time in the half for Thauvin to test Markovic with a deflected effort from range, but a lively first 45 minutes somehow ended goalless. As if to compensate, the second period started in dramatic fashion, as half-time Slavia substitute Mikulas Konecny found himself in hot water straight away, sent off for denying a goal-scoring opportunity after a lengthy VAR review.
Thauvin came close from the resulting free-kick, but a defiant home side were soon on the attack, and Šturm whipped the ball into the top corner to turn agony into ecstasy for the supporters.
A Lens onslaught inevitably arrived, and only a goalline clearance from Tomas Vlcek denied Thauvin a quick equaliser, before substitute Odsonne Edouard directed a header straight at Markovic a little later.
But Dino Toppmoller’s side eventually found a way through the defiant rearguard action, and there was a sense of cruel inevitability that it was Sima who swept it in. But the drama was far from over, as Sturm struck again in dramatic fashion to restore the lead for Slavia, sweeping home after pinball in the box from a free-kick.
The hosts’ joy was short-lived, though, as a fresh dose of heartbreak saw Thauvin find another equaliser, guiding a neat header past Markovic in the 91st minute.
By that point, the game had descended into total chaos, and Aguilar dealt a final, killer blow when he found the bottom corner from the edge of the box even deeper into stoppage time.
That secured Lens’ first win on the road in Europe since September 2005, while they have also stretched their unbeaten run in European openers to five matches (W1, D4). Slavia are without a win in their last 16 games in UEFA competitions (D5, L11), although they will wonder quite how that didn’t change here.
Flashscore Man of the Match: Florian Thauvin (Lens)